1. Field of the Invention
The present invention relates to gas phase polymerization using modified carbon black and further relates to the products made from gas phase polymerization using modified carbon black.
2. Discussion of the Related Art
Gas phase polymerization has been described as a means of polymerizing polymers such as ethylene/propylene diene monomer (EPDM) and diene-type polymers such as butadiene rubber, without the use of solvents. One advantage of this approach is the lower cost of the resulting polymer because there is no need to recover and recycle solvents. Another advantage is the granular form of the polymer which facilitates mixing of the polymer, e.g., elastomer, with the other ingredients in a formulation. One problem encountered in gas-phase polymerization which must be overcome is the tendency of the polymer particles formed in the gas phase to stick together in the reactor, thereby giving undesirably large lumps of polymer. This problem has led to the term "sticky polymer" which has been defined as a polymer being particulate at temperatures below the sticking or softening temperature but forming agglomerates at temperatures above the sticking or softening temperature. Sticking of the polymer particles has been prevented at times by incorporating filler materials such as carbon black, silica, and clay in the polymerization process which functions as a partitioning agent to keep the polymeric particles separated. The surface chemistries of these filler materials can be very important since the filler materials have the ability to influence the efficiency of the fillers to function as partitioning agents and can affect the efficiency of the polymerization catalyst that is present in gas-phase polymerization. In some cases, attempts have been made to alter the surface properties of the fillers to achieve the necessary partitioning properties and to reduce or eliminate the filler's effects on the polymerization catalyst.
However, there is a need to find improved fillers which act as acceptable partitioning agents, thus keeping the polymeric particles separated and, preferably affecting the resulting polymer in such a way as to improve its properties.